There is a technology for performing communication between a base station disposed at each of a plurality of principal localities defined in advance and a communication terminal present at an arbitrary location. In a case where reliable communication between the base station and the communication terminal is desired, it is conceivable to use satellite communication or the like, while a communication system using satellite communication is expensive. Accordingly, in order to perform communication over a long distance at low cost, a communication technique utilizing the reflection of radio waves at the ionosphere is used.
Japanese Laid-open Patent Publication No. 07-322352 and Japanese Laid-open Patent Publication No. 55-147842 are disclosed as related art.